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Öğe Bio-derived catalysts for hydrogen production: Synthesis, characterization, and performance(Elsevier BV, 2025-03) Arzu Ekinci; Ömer Şahin; Gurbet Canpolat; Orhan BaytarIn this study, green synthesis method was used to prepare Co–La–B catalysts using Rheum ribes bark extract as stabilizing agent. SEM, EDX, XRD, FTIR, TEM and XPS analyses determined the structural and morphological properties of the Co–La–B catalyst. The average particle size was found to be about 30 nm, indicating a high surface area, which can enhance the catalytic activity. In addition, the presence of functional groups in the shell extract was confirmed, suggesting their role in stabilizing the metal particles during synthesis. The particle size was determined to be 20–50 nm in TEM analysis results. For the first time, green synthesis of Co–La–B catalyst using Rheum ribes bark extract was carried out and the effect of different NaOH/NaBH4 concentrations, different amounts of catalyst and temperature on sodium borohydride hydrolysis was studied. In the study, the cycle frequency (TOF) values for Co–La–B catalyst at different temperatures were determined to be 31610 mLH2/gcat.min. Activation energy (Ea), activation entropy (ΔS) and activation enthalpy (ΔH) values were calculated as 62.61 kJ/mol, −120 J/molK and 29.82 kJ/mol, respectively. Reusability tests determined the efficiency of the nanoparticle as 89.4 %.Öğe Eco-friendly biosynthesized silver, copper, and nickel nanoparticles mediated Rheum ribes: Assessment of their cytotoxicity and antimicrobial activity(Elsevier BV, 2025-02) Bahri Gür; Mustafa Cengiz; Canan Vejselova Sezer; Orhan Baytar; Ömer Şahin; Adnan Ayhanci; Hatice Mehtap KutluBackground: The green synthesis of metallic nanoparticles has recently become a research area of increasing interest due to their potential applications in nanomedicine. Aim of study: This study aimed to investigate, for the first time, the anticancer properties of silver nanoparticles (Ag-NPs), copper oxide nanoparticles (CuO-NPs), and nickel oxide nanoparticles (NiO-NPs) on A549 and Beas-2B cell lines, as well as their antibacterial efficacy against Escherichia coli and Staphylococcus aureus strains, synthesized through a green synthesis approach utilizing Rheum ribes plant extract. Methodology: The current study introduces a sustainable and environmentally friendly method for the biosynthesis of Ag-NPs, CuO-NPs, and NiO-NPs utilizing the aqueous extract of Rhubarb (Rheum ribes). The spectroscopic and morphological properties of the Ag-NPs, CuO-NPs, and NiO-NPs obtained from the Rheum ribes extract were confirmed using different analytical techniques. Results: The Ag-NPs, CuO-NPs, and NiO-NPs exhibited different morphology with a size of about 7.90, 12.0, and 12.63 nm, respectively, and were free of impurities and highly stable particles. In addition, the NPs were further investigated for their anticancer and antibacterial properties. The anticancer effects of the NPs were assessed using the MTT assay and confocal microscopy in non-small cell lung cancer (A549) and healthy lung (Beas-2B) cells. The study results demonstrated that Ag-NPs, CuO-NPs, and NiO-NPs had cytotoxic effects on A549 cells that were concentration-based, having IC50 values of 4.16, 21.28, and 37.68 μg/mL, in that order. Additionally, it was observed that the above-mentioned NPs exhibited strong activity against bacteria. Conclusions: The nanoparticles derived from Rheum ribes extract appear to hold great potential as a class of nano-biomaterials intended for usage in biological fields.Öğe Eco-friendly nanocatalysts for hydrogen generation via sodium borohydride hydrolysis and enhanced fuel cell applications(Elsevier BV, 2025-04) Arzu Ekinci; Ömer Şahin; Sevnur Turgut; Orhan BaytarSodium borohydride (NaBH4) hydrolysis is a promising method for sustainable hydrogen production, but its efficiency depends on high-performance and eco-friendly catalysts. This study introduces a green hydrothermal synthesis using tobacco stem extract to fabricate Co–Sb nanoparticles, reducing toxic chemical usage compared to conventional methods. Catalytic tests confirm their high efficiency in NaBH4 hydrolysis, with hydrogen generation increasing at higher temperatures and NaOH/NaBH4 concentrations. Structural analyses (XRD, FT-IR, SEM, TEM) reveal an amorphous, porous morphology with spherical particles (∼20–30 nm). Co–Sb nanoparticles achieve a hydrogen generation rate of 5618 mlmin−1g−1, surpassing Co nanoparticles (5360 mlmin−1g−1), with lower activation energy (30.9 kJ mol−1 vs. 35.5 kJ mol−1), highlighting Co–Sb's superior catalytic efficiency—additionally, 1 wt% Sb doping enhances hydrogen production and improves PEM fuel cell performance, reaching a peak power density of 137.3 mW/cm2. However, reusability tests of the Co–Sb catalyst revealed a decline in the hydrogen generation rate, indicating catalyst deactivation due to oxidation on active surfaces and the accumulation of by-products. Furthermore, excessive Sb doping was found to block active sites on the catalyst surface, thereby reducing its efficiency. This study underscores the viability of green-synthesized Co–Sb nanoparticles for hydrogen generation and fuel cell applications, offering a sustainable alternative to energy technologies.Öğe Green-synthesized ZrFeO nanoparticles as efficient cathode materials in PEM fuel cells(Elsevier BV, 2025-01) Suna Tarhan; Arzu Ekinci; Orhan Baytar; Abdurrahman Akdag; Ömer ŞahinThis study explores the application of ZrFeO nanoparticles, synthesized from fig leaf extract through a green synthesis method, as cathode materials for PEM fuel cells. The nanoparticles, doped with FeO and varying Zr ratios, were combined with Pt metal and characterized using XRD, SEM, EDX, and TEM to analyze their structural and morphological properties. The particle sizes for FeO and Zr-doped FeO were determined to be 2 nm and 2.5 nm, respectively. The electrochemical active surface areas of the catalysts—Pt-FeO/C and Zr-doped variants (PtFeO/C-1 wt%Zr, PtFeO/C-5 wt%Zr, and PtFeO/C-10 wt%Zr)—were measured as 97, 154, 138, and 119 m2/gPt, respectively, demonstrating a significant enhancement in surface area with the incorporation of Zr at optimal doping levels. Catalyst retention after 250 cycles was 29% for Pt–FeO/C, 60% for 1 wt% Zr-doped Pt–ZrFeO/C, 93% for 5 wt% Zr-doped Pt–ZrFeO, and 71% for 10 wt% Zr-doped Pt–ZrFeO. Performance testing at 70 °C revealed a hierarchy of catalytic activity: Pt–ZrFeO/C > Pt–FeO/C > Pt/C. The findings highlight the potential of green-synthesized ZrFeO nanoparticles as effective support materials for cathode catalysts, offering improved performance in PEM fuel cells while markedly reducing platinum dependency. This innovative approach integrates environmental sustainability with technological progress in fuel cell applications.
